The invention relates to a harness for use with breathing apparatus. In particular, the invention relates to a harness of the type worn by professional fire-fighters, though it may be applied to other sorts of harness, such as a diving harness, also.
A known harness 1 for use with breathing apparatus is shown in FIG. 1. The harness includes a back plate 2, a waist belt 3, shoulder straps 4 and shoulder pads 5. A gas cylinder 6 containing pressurized gas is mounted to the back plate 2. The weight of the harness and cylinder is transferred to the hips of the user through the waist belt 3 and to the upper body of the user through the shoulder pads 5 and shoulder straps 4.
In this regard, each shoulder strap 4 is attached in two places. Namely, at a first end to one of the shoulder pads 5 and at a second end to the lower part of the back plate 2. Each strap thus forms a loop, which takes some of the weight of the harness/cylinder unit and helps to hug the harness to the wearer's body.
The constant tension on the shoulders from the shoulder straps 4 makes wearing the harness 1 noticeable and can cause fatigue. In addition, when the wearer lifts an arm into the air, the shoulder strap 4 goes into tension, restricting movement and causing the associated shoulder pad 5 to dig into the wearer's shoulder. This is a particular problem when climbing ladders, reaching for high objects or crawling.
Furthermore, when the wearer is crawling one shoulder drops as the other arm is stretched out and this can cause tension in the strap 4 on the shoulder which drops to be completely removed. The shoulder strap and associated pad 5 can therefore fall off the shoulder making the unit unstable.
A known harness designed to alleviate the above problems is described in U.S. Pat. No. 6,290,111. In this harness, the shoulder straps are attached to opposite sides of a rigid element provided at the lower part of the back plate. The rigid element is pivotally connected to the back plate at a central point between where the shoulder straps are attached. Thus, when the wearer raises one arm the tension in the associated shoulder strap causes the rigid element to rotate about the central point, helping to reduce the tension in the strap. Furthermore, rotation of the rigid element causes tension to be applied to the other shoulder strap, helping to prevent the tension in that shoulder strap from being removed. However, the above harness allows only a limited degree of movement in which tension in the straps is accommodated, and tension is not always maintained in both straps which can make the harness unstable.
It is therefore desirable to provide a harness which enables the wearer to perform a fuller range of movement, in comfort, and which prevents the harness from becoming unstable.
According to the present invention, there is provided a harness for use with breathing apparatus, comprising: a back plate; two support straps, each of which extends between an upper part of the back plate and a lower part of the back plate, the two support straps being disposed on opposite sides of a central axis of the back plate; and a tension equalizing mechanism connected to the support straps and being arranged such that, when tension is applied to a first strap of the support straps, it acts to transfer the tension to the other, second strap, thereby increasing the tension in the second strap, the tension equalizing mechanism being resiliently biased towards a neutral configuration.
The resilient biasing of the tension equalizing mechanism towards the neutral configuration ensures that the support straps move with the body and remain tense. In this way, the harness is prevented from becoming unstable.
Preferably, the tension equalizing mechanism is arranged such that, when tension is no longer applied to the first strap, it acts to increase the tension in the first strap by decreasing the tension in the second strap and transferring the tension to the first strap.
Thus, the support straps are stopped from going slack and are always kept under tension, ensuring that the straps do not come off the user's shoulder during use of the harness.
Preferably, the tension equalizing mechanism includes first and second tension accommodating means connected by a connecting element, wherein, when tension is applied to the first support strap, the first tension accommodating means acts to increase an effective length of the first support strap and to reduce the tension in the strap, and the tension is transferred via the connecting element to the second tension accommodating means, which acts to reduce an effective length of the second support strap and to increase the tension in the second support strap.
The independent action of each of the first and second tension accommodating means on the first and second support straps, together with the connection therebetween, enables the wearer to perform a fuller range of movement and in greater comfort than previously possible. In addition, it ensures that the harness is stable when the user is crawling.
By enabling the wearer to move more freely and with less restriction, the harness advantageously allows the wearer to concentrate on the task at hand without having to worry about pain and stress caused by carrying the weight of the cylinder in an uncomfortable manner.
Preferably, first biasing means for urging the first attachment means to a central return position and/or second biasing means for urging the second attachment means to a central return position are provided, so as to resiliently bias the tension equalizing mechanism towards the neutral configuration. The biasing means may include an elastic return part such as a rubber return part or a spring.
Advantageously, the biasing means provide a small, controlled resistance to the movement of the wearer, making the adjustment of the shoulder straps feel more natural and secure to the wearer and ensuring that adequate tension is always provided in the straps.